The objectives of this project are to investigate relationships among differences in personality, sensory thresholds, reaction time, and autonomic nervous system (ANS) activity in normal humans. Bilateral skin conductance and heart rate have been recorded in sessions in which constant and variable intensity tones and lights are presented, in which auditory and two-flash thresholds (TFT) are determined by methods which permit signal detection analyses and in which simple reaction time is measured. Several standardized personality tests were also given. These include scales of sensation-seeking, the Eysenck scales of extraversion, neuroticism, and psychoticism field dependence and anxiety. In addition comprehensive measures of lateral dominance have been given. A procedure for manipulating ANS arousal experimentally with minimal distracting effects - a change in posture from supine to standing - was used to study such problems as the effects of base levels on responsivity, the effects of arousal on performance, and the effects of personality variables on this relationship. This project allows testing of several theoretical models of the relationships of ANS activity, sensory sensitivity, and personality, some of which have implications for the etiology of psychopathology. Recently, personality variables assessed chiefly from the Eysenck scales and a measure of impulsivity have been correlated with ANS activity in normal children and adolescents. The most consistent results are negative correlations between Extraversion and the magnitudes of electrodermal responses to nonsignal and signal stimuli, confirming results on adults from other laboratories. A measure of behavioral impulsivity correlated positively with magnitudes to signal stimuli. Extraversion also correlated negatively with reaction time, confirming a previous result from this laboratory.